America has not been supplanted as the dominant global power.
There is a tendency to make too much of American shortcomings. By comparing what we have by a standard of what we purportedly must achieve, you can say America's military is unready, for example. While there is real value in that kind of analysis, don't get carried away and say our military is poor. By those metrics, a very good but too small military is rated poorly. Which would be critical if your enemy is across your border. We don't face that problem.
Also, war is waged not against our aspirations but against enemies. They have problems that are hard to see. As Russia has demonstrated this year so clearly. China's military isn't as good as their shiny weapons advertise, either.
Putin believed he could fracture NATO by invading Ukraine. He misjudged the relationship and has since gone all mega paranoid seeing an American plot in his ... difficulties. I have not worried about America's commitment to Europe:
Moscow also failed to understand America’s relationship with Europe. Time and again, Europeans bemoaned that Washington had abandoned its European commitments. That that was never the case didn’t stop U.S. think tanks from validating the idea, nor did it dissuade Russia from believing it. In times of peace, the U.S. could do without the prior relationship with Europe, bickering over trade rules and Russian energy dependence. But when the war broke out, the relationship rapidly transformed.
Trump didn't wreck our ties to Europe and Biden isn't so addled that we forgot our ties.
Europe is an objective to defend as well as a source of allies. But our attention varies with the threat to Europe. Putin made us pay attention:
Good grief, if Putin had just kept his mouth shut and his army at home, NATO would have continued to disarm.
And Putin took China's "no limits"
partnership seriously, when China values trade ties with America more
than it values Russian territorial ambitions in Europe. Back to the analysis I quoted initially:
The past few months haven’t taught us that the United States is finagling a new world order. It’s taught us that Russia is weakening, that China is managing its relationship with the U.S. carefully, and that the international architecture created after World War II, though more complex, essentially remains in place. It is a unipolar world.
Remember, even with much greater power, China--our "pacing threat" for judging our military capabilities--has other threats that soak up its power. A problem thus far we don't have.
The American century is not over.
NOTE: War updates continue here.